1. Field of the Invention
The present invention relates to an optical system, a method for focusing the optical system, and an imaging apparatus equipped therewith.
2. Related Background Art
There has been proposed an internal-focusing type optical system suitable for a film camera, an electronic still camera, a video camera, and the like as disclosed in such as Japanese Patent Application Laid-Open Nos. 7-199066, 3-200909.
In the conventional internal-focusing type optical systems, since refractive power balance between the focusing lens group and the other lens groups has not been optimized and specifications of optical glasses of the lenses composing the focusing lens group have not been optimized, it has been difficult to secure high focusing performance with keeping excellent optical performance over entire focusing range from infinity to a close distance.